A variety of manufacturers currently offer filtering devices for filtering drinking water which include replaceable filter cartridges. Typically, activated charcoal is the major filtering agent. In some devices the filter may be directly hooked to a faucet or along a line feeding a faucet. In others water is gravity fed from a storage container or other reservoir through the filter cartridge at a relatively low pressure.
A number of manufacturing techniques have been used previously to assemble such filter cartridges. Components of the cartridge may be screwed together, sonically welded and/or solvent bonded. Each approach has its disadvantages.
Screw-together components are relatively expensive to manufacture as threads must be provided. Even where plastic components are used, complicated molds or complicated fabricating techniques must be employed to form the threads and/or remove a molded threaded component from the mold.
Sonically welded components require additional sonic bonding equipment to perform the sonic bonding step. Moreover, the sonic bond must be tested or multiple sonic bonds provided to assure sealing.
Solvent bonding of components is perhaps the least expensive. However, it is also the least desirable since the solvents can enter the filtration agent and contaminate the cartridge. Solvent bonding is particularly undesirable for cartridges which are being used to filter drinking water.